Preparation of aryldialkyl peroxides



Patented Feb. 2, 1954 BREBARATIQN F ARYLDIALKYIJ PEEOXIDES Hamid Bcardman, Hercules. Powder Wilmington, Delz, assignor to Company, Wilmington,- Deli,

7 acorpcraiicnof. Delaware No Drawing; Application July 1, 1950, Serial No. 1.7 .1745.

11 (31311118,. (Cl. 260-6I0)' This invention. relates to; the; condensation. of

hxdr nercxides; and; more particularly e aryialiryi hxdroperoxides with warm tertiary alcohols and rid the: peroxides so produced.

The. reaction between aliphatic tertiary. alco. hols and alkyl hydrop roxides. for the production Q llmmetrical peroxides: is known... The condens-ation involv d requires that the: reaction be carried out. the; presence of. as least. suflicient concentrated aqueous acid. solutions to act as: a solvent for the: aliphatic tertiary alooholsfcr, in the case of: suliuric acid the: tertiarylc hol it self. man be. combined as. a suliuric. acid: ester. and that ester may some. produced; by dissolving the, corresponding olefin, coneeriirated aqueous sol-tune acid. Qnhi the presence (if-stron acids can these alcohols thus. be condensed. with alien hydroperoxidesi. But ihe presence oi the required. concentration, or acid catalysir-d-aryla hydropercxides. such. as: e ardialkyl ja-arylmethyl: nydropercxides. incapable of; underreaction to.- form; peroxides hecausehydro peroxides oi this type: deco rmose into phenolic compounds. the presence. or. the stron acid solxgent. Thus; it. is. not P ssible eiten; by modifiying the catalyst concentration. to produce e-arylalkxl dalkyl. peroxide by condensation of. an; errand allrxl hydroperoxide with, a. tertiary aliphatic alcoholl nor is: it. possible to. produce bisie-aryle alkali peroxides Icy condemn}: the corresponding alcohol and hydroperoxide in the; manner used n. the prior art for aliphatic peroxidfi'. I

Now in accordance withihe present invention; it has been found that -arylalk3d beroiiides: of theiormula radical. radical... and either: an aliphatic. or oral: radical; can. he: produced by reacting? a h-ydm R minds of: the fiormula at. tor-i520 the presence. or etalghc amount up to cow-or an acid-acting ndensa 2 tion. catalyst based on the. weight. of the alcohol.

While. the. present invention provides a process by which. for he. first time, it has. been possible to condense a,a-d'ialkyl-a-arylmethy1 hydroponoxides with a-aralkyl alcohols. the process is also applicable for th condensation of aliphatic tertiary hydroperoxid'es with c-aralkyl alcohols which are more susceptible to dehydration in strong; acid, solutions of. the prior art.

The following examples constitute, specific lllustrations of the manner in. which these novel a-arylalkyl peroxides may be produced. All parts are. parts. by weight.

Example I To 150,000 parts: a,e-dimethylbenzyl alcohol, free of acetophenone, was. added 8 parts p-toluenesulfonic acid. When dissolution was complete, 50,000 parts a,e-dimethylbenzyl hydroperoxide was added and the solution was heated ina constant temperature: bath at 115 C. for 2 /9, hours. All but 13 of the hydroperoxide had re+ acted. The: solution was, nevertheless, washed with 10% sodium carbonate to remove the catal yst, and excess alcoholwas removed by heating at alcout 100C: and 3: mm. pressure. To the residue was: added 3: volumes of pentane and the solutionwas held? at 10 C. to crystallize. The crystals obtained in the lirsi: crop amounted to 303,000 parts... These were bis (-c,a-dimethylbenzyl)* peroxide, melting point 36.l-36'.4 C;

Example II Example 1. was; repeated using as the catalyst aqueous. sulfuric acid based. onthe mc-dimethylbenzyl alcohol and approximately a kmole. excess of. cie-dimethylbenzyl hydro er xid A temperature or: 90 d.v was used-tor the reaction. After 4 /2 hours of thehydroperoxide had disappeared and of the hydroperoxide was converted tobis(a,ci-dimethylbenzyl) peroxide.

Example Ill fluoride etherate as the catalyst based on the c,c-dimethylbenzyl alcohol. The yield of peroxide based on hydroperoxide was 76% of theory.

Emmple IV I I A solution of 72,000 parts w,adimethyl-p methylbenzyl alcohol and 35,000 parts mos-(iii methylbenzyl hydroperoxide containing dissolved therein 7 parts p-toluenesulfonic acid was heated for 2. hours at C. Allbut 11% of the hydroperoxide had disappeared at the end of this time and the yield of crude e,a-dimethyl-p-methylbenzyl a,a-dimethylbenzyl peroxide based on hydroperoxide reacted was 68%. This product could not be crystallized in the usual manner.

Example V A solution of 50,000 parts commercial 60% t-butyl hydroperoxide, 50,000 parts a,a-dimethylbenzyl alcohol and 10 parts p-toluenesulfonic acid monohydrate was heated at 90 C. for 7 hours. All of the hydroperoxide disappeared. The volatiles were removed at 70 C. and 1 mm. pressure. The residue was crystallized from pentane at l C. to obtain a dimethylbenzyl t-butyl peroxide, melting point 155 (3.

Example VI A solution of 1000 parts a,a-dimethyl-p-methylbenzyl hydroperoxide and 2000 parts e a-dimethyl-p-methylbenzyl alcohol containing dissolved therein 6 parts of p-toluenesulfonic acid monohydrate was heated at 80 C. for 3 hours. All of the hydroperoxide disappeared during this heating period. The resulting solution was washed with a sodium carbonate solution and unreacted alcohol was distilled off at 1 mm. pressure. The residue was dissolved in 3 volumes of methanol and cooled to 10 C. to obtain bis(a,a-dimethyl-p-methylbenzyll peroxide as a white crystalline material melting at 54 C. The

yield was 80% of the theoretical.

The bis(a-arylalkyl) peroxides which are produced in the process of this invention are symmetrical or unsymmetrical peroxides of the formula where Ar represents aryl groups or substituted aryl groups such as phenyl, naphthyl (aor /3-), Ar-tetrahydronaphthyl, tolyl, ethylphenyl and other alkyd-substituted phenyl groups, where R is a group which may be the same or different and represents aliphatic hydrocarbon radicals R-O-OOH and alcohols having the general formula AI(JOH R! where Ar, R, and R. are the same as for the general formula for the peroxide above.

The hydroperoxides of the general formula 4 can be made by oxidation of an organic compound of the general formula in which Ar, R, and R represent the previously disclosed radicals. The process of oxidation is well known in the art and comprises essentially passing a gas containing free oxygen such as air through the organic hydrocarbon compound in the liquid state at, for example, about 70 C. to 0., preferably in the presence of a hydroperoxide stabilizer such as dilute alkali, until between about 5 and 50% hydroperoxide based on the hydrocarbon is formed. The hydroperoxide may be concentrated through removal by reduced pressure distillation of the .unoxidized fraction and any low-boiling icy-products, and may be separated for further purification by forming a crystalline complex with sodium hy droxide or an amine such as aniline which can be separated by filtration in a state of high purity. The hydroperoxide can then be liberated from the crystalline complex by shaking withthe calculated amount of dilute mineral acid to combine with the alkali or amine. The e-arylalkyl hydroperoxide separates from the aqueous phase as a substantially pure oily hydroperoxide which may be washed again with water and be used directly in accordance with this invention for conversion to the peroxides by condensation with the arylalkyl alcohols.

The aryl alcohols useful in accordance with the process of this invention may be prepared by well-known methods and include a,a-dimethylbenzyl alcohol, a,e-dimethyl p methylbenzyl alcohol, a,c-diphenyl ethanol, and the like. 1

As a catalyst, any of the wellknown acid-act ing condensation catalysts may'be used, such as the Friedel-Crafts type catalysts including boron trifluoride, complexes of boron trifluoride with ethers and organic acids, halides of metals whose hydroxides are amphoteric, such as aluminum chloride, zinc chloride, stannic chloride, titanium tetrachloride, etc, and mineral acid condensation catalysts, such as hydrofluoric acid, fluoboric acid, sulfuric acid, and phosphoric acid, and'the organic sulfuric and su1-- fonic acids, such as the acid sulfate of the alcohol being condensed, or aromatic sulfonic acids including benzene, toluene, and naphthalene sulfonic acids.

The amount of catalyst used in this invention is critical in that too concentrated an acid medium will cause decomposition of the hydroperoxide. The maximum amount of catalyst that can be used with the aryl methyl hydroperoxides is-based on the alcohol since an excess of-alcohol will ordinarily diminish the activity of the catalyst toward decomposition of the hydroperoxide and provide sufficient concentration. of alcohol that reaction of the hydroperoxide with the alcohol becomes the major reaction. On the basis that at least the theoretical amount and not more than a two-fold excess of alcohol will be present, the maximum amount of catalyst that will give satisfactoryyields of peroxide as the major product is 0.5% based on the weight of the alcohol. The minimum amount Will be an amount sufilcient to catalyze the reaction, and that amount will vary with the activity of the catalyst. in the, caseof'any .of the acid;x

acting condensation catalysts, as little as 0.001%,

will be operable at a satisfactory rate of condensation.

As stated above, the amount of alcohol present in the condensation should be at least the theoretical calculated amount to combine with all of the hydroperoxide. An excess is preferred but more than three times theoretical or a twofold excess is objectionable, since a larger excess reduces the yield based on the alcohol due to losses of alcohol.

The temperature for the condensation must be at least 50 C. in view of the low catalyst concentration but must be kept below 120 C. because of a tendency for the aryl methyl hydroperoxides to pyrolyze rather than condense with the alcohol. The preferred temperature range for the minimum of side reactions is 70 C. to 100 C.

The symmetrical biS(a a-dialkyl-a-arylmethyl) peroxides produced by the process of this inven tion may also be produced in accordance with the copending application of Eugene J. Lorand and John E. Reese filed on even date herewith. The unsymmetrical peroxides made by the present invention have not heretofore been described and the present invention provides the first practical process for their production. The peroxides of the present invention find a number of commercial applications. Those peroxides of the general formula, in which Ar represents a phenyl or alkylated phenyl radical, have unusually good characteristics for use as catalysts in polymerization processes, halogenation reactions, etc., where high heat stability is desired. The bis(a,a-dialkyl-a-arylmethyl) peroxides are also useful in synthesis. They may, for example, be reduced by hydrogenolysis to the corresponding tertiary alcohols.

What I claim and desire to protect by Letters Patent is:

l. The method of preparing a peroxide of the formula wherein Ar is an aryl radical, R is an aliphatic radical, and R is a radical of the group consisting of aliphatic and aryl radicals differing from Ar, which comprises reacting a hydroperoxide of the formula but not exceeding a two-mole excess of an alcohol of the formula 6 at 50-120 C. in the presence of a catalytic amount up to 0.5% of an acid-acting condensation catalyst based on the weight of the alcohol.

2. The process of claim 1 in which the alcohol is a,a-dimethylbenzyl alcohol and the hydroperoxide is a,a-dimethylbenzyl hydroperoxide.

3. The process of claim 1 in which the alcohol is a,a-dimethyl-p-methylbenzyl alcohol and the hydroperoxide is a,a-dimethylbenzyl hydroperoxide.

4. The process of claim 1 in which the alcohol is a,a.-dimethylbenzyl alcohol and th hydroperoxide is t-butyl hydroperoxide.

5. The process of claim 1 in which the alcohol is a,a-dimethylbenzyl alcohol and the hydroperoxide is a,a-dimethyl-p-methylbenzy1 hydroperoxide.

6. The process of claim 1 in which the condensation catalyst is an aryl sulfonic acid.

7. The process of claim 1 in which the condensation catalyst is p-toluenesulfonic acid.

8. The process of claim 1 in which the condensation catalyst is a boron trifiuoride catalyst.

9. As a new composition of matter an unsymmetrical peroxide of the formula wherein Ar is an aryl radical, R is an aliphatic radical and R is a radical of the group consisting of aliphatic radicals and aryl radicals difiering from Ar.

10. As a new composition of matter, t a-dimethylbenzyl t-butyl peroxide.

11. As a new composition of matter, a,a-dimethylbenzyl a,a-dimethyl-p-methylbenzy1 peroxide.

HAROLD BOARDMAN. 

1. THE METHOD OF PREPARING A PEROXIDE OF THE FORMULA 